Tamerlan and Dzhokhar Tsarnaev carried out the terror attack that left three dead and countless injured at the 2013 Boston Marathon on April 15. Late at night on Thursday, April 18, as the manhunt heated up, the brothers shot Collier, a 26-year-old police officer at the Massachusetts Institute of Technology, to death.

The pursuit led to Watertown, where Dzhokhar Tsarnaev, then 19, ran over his older brother overnight, killing him. After the younger Tsarnaev was found hiding in a boat, he was charged, and ultimately convicted, of 30 federal charges related to the terror attack and Collier's murder.